Variable-density thinning designs for harvester-based operations in Northern Europe

Abstract

ABSTRACT Variable-density thinning (VDT) can be used to start the conversion of young homogeneous conifer plantations to the single-tree selection system. A design for VDT is presented, which is adapted to harvester-based operations in northern Europe without prior tree marking and the low target diameters in the region. Six treatment cells with a size of 10 × 10 m are placed along a 30 m stretch of a strip road with treatments gap (removing all but understory trees), skip (no thinning), and four treatment cells with crop tree-based crown thinning, which removes two dominant competitors of 1–4 crop trees per cell. Skips might in later thinnings be converted into gaps, which is why skips and gaps are placed systematically in the 2 × 3 treatment blocks. Assignment of the crop tree number variants to treatment cells are decided by the harvester operator based on the given stand structure and presence of crop trees meeting all selection criteria. So far, five operations have confirmed the practicality of this design and given some insight into the learning process of harvester operators with these new methods.